This study was undertaken to characterize the ubiquitin proteasome system (UPS) response to varied dietary protein intake, energy deficit (ED), and consumption of a mixed meal. A randomized, controlled trial of 39 adults consuming protein at 0.8 (recommended dietary allowance [RDA]), 1.6 (2×-RDA), or 2.4 (3×-RDA) g · kg(-1) · d(-1) for 31 d. A 10-d weight maintenance (WM) period was followed by 21 d of 40% ED. Ubiquitin (Ub)-mediated proteolysis and associated gene expression were assessed in the postabsorptive (fasted) and postprandial (fed; 480 kcal, 20 g protein) states after WM and ED by using muscle biopsies, fluorescence-based assays, immunoblot analysis, and real-time qRT-PCR. In the assessment of UPS responses to varied protein intakes, ED, and feeding, the RDA, WM, and fasted measures served as appropriate controls. ED resulted in the up-regulation of UPS-associated gene expression, as mRNA expression of the atrogenes muscle RING finger-1 (MuRF1) and atrogin-1 were 1.2- and 1.3-fold higher (P<0.05) for ED than for WM. However, mixed-meal consumption attenuated UPS-mediated proteolysis, independent of energy status or dietary protein, as the activities of the 26S proteasome subunits β1, β2, and β5 were lower (P<0.05) for fed than for fasted. Muscle protein ubiquitylation was also 45% lower (P<0.05) for fed than for fasted, regardless of dietary protein and energy manipulations. Independent of habitual protein intake and despite increased MuRF1 and atrogin-1 mRNA expression during ED, consuming a protein-containing mixed meal attenuates Ub-mediated proteolysis.

译文

这项研究旨在表征泛素蛋白酶体系统 (UPS) 对不同饮食蛋白质摄入,能量不足 (ED) 和混合餐消费的反应。一项随机对照试验,研究了39名成年人在0.8时摄入蛋白质 (推荐膳食津贴 [RDA]),1.6 (2 ×-RDA),或2.4 (3 ×-RDA) g · kg(-1) · d(-1) 持续31 d。10 d体重维持 (WM) 期之后是21 d的40% ED。通过使用肌肉活检,基于荧光的测定,免疫印迹分析和实时qRT-PCR,在WM和ED后的吸收后 (禁食) 和餐后 (进食; 480 kcal,20g蛋白) 状态下评估泛素 (Ub) 介导的蛋白水解和相关基因表达。在评估UPS对不同蛋白质摄入量,ED和喂养的反应时,RDA,WM和禁食措施可作为适当的对照。ED导致UPS相关基因表达的上调,因为ED的atrogenes肌肉环指-1 (MuRF1) 和atrogin-1的mRNA表达比WM高1.2和1.3倍 (P<0.05)。然而,混合膳食消耗减弱了UPS介导的蛋白水解,与能量状态或饮食蛋白质无关,因为饲喂的26s蛋白酶体亚基 β1、 β2和 β5的活性低于禁食 (P<0.05)。无论饮食中的蛋白质和能量操作如何,进食的肌肉蛋白泛素化也45% 低于禁食的肌肉蛋白泛素化 (P<0.05)。与习惯性蛋白质摄入无关,尽管ED期间MuRF1和atrogin-1 mRNA表达增加,但食用含蛋白质的混合餐会减弱Ub介导的蛋白水解。

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